The overwhelming majority of cycles, including motorcycles and bicycles, made, sold and used throughout the world utilize a drive train with a conventional chain providing power between a first pulley operatively associated with a drive shaft and a second pulley operatively associated with a hub of a rear wheel. In bicycle applications, the first pulley is operatively associated with a crank set. These chains are relatively effective at transmitting power between the first and second pulleys, but they are not without shortcomings. The shortcomings include, but are not limited to, the need to periodically be lubricated, the fact that with wear the chains become less efficient in transmitting power, debris can lodge between chain links diminishing efficiency, the chains stretch with extended use and need to be periodically replaced and may further wear the teeth of the first or second pulleys requiring their replacement as well and chains can be noisy.
One known alternative to chain-based drive train systems are belt drive train systems. Belt drive systems overcome a number of the problems discussed above, but are not without their own problems. For example, belt drive systems generally require relatively precise alignment between first and second pulleys of the belt drive system. Providing such alignment can be difficult particularly in bicycles, where crank sets and hubs of various manufacturers can be mixed and matched in bicycle assembly, resulting in less than precise alignment. In addition, incidents may happen during use of the bike that degrades the alignment. As a result of a loss of a precise alignment, the belts of known belt drive systems can wander relative to the pulley and fall off the pulley. This problem is exacerbated because the belts and pulleys are relatively narrow relative to the belt length. One known way of addressing this misalignment is to provide one or more radially extending side flanges around the circumference of the pulley to prevent the belt from wandering off the pulley. However, such side flanges, particularly where two side flanges are provided, complicate the manufacture of the pulley, increase weight, make the pulley wider and increases the cost of the pulleys. A further problem with known belt drive systems is collection of debris between teeth of the pulleys which can interfere with effective force transmission and, in extreme cases, cause a belt to slip off a pulley. Each of these disadvantages is significant for cycle applications and particularly bicycle applications.
The various embodiments described herein are intended to overcome one or more of the problems discussed above.